1. Coding, capacity and duration of memory

• What is coding?

  The format in which information is stored in various memory stores
• What is the capacity?


  The amount of information that can be held in a memory store
• What is the duration?


  The length of time information can be held in memory
• What is short term memory?

  • The limited capacity memory store
  • Coding is acoustic
  • Capacity is between 5-9 items
  • Duration is between 18-30 secs
• What is long term memory?


  • The permanent memory store
  • Coding is semantic
  • Unlimited capacity
  • Can store memories for up to a lifetime
• Who researched into the coding of STM and LTM?

  Baddeley
• Describe research into the coding of STM and LTM (Baddeley)

  • Give list of different words for groups for participants to remember
  • Groups = acoustically similar, acoustically dissimilar, semantically similar, semantically dissimilar
  • Participants were shown the words and asked to recall in order
  • Immediate recall (STM recall): worse on acoustically similar words
  • 20 mins (LTM recall): worse on semantically similar words
  • Info is coded semantically in LTM
• Who researched into the capacity of STM?

  Jacobs
• Describe research into the capacity of STM (Jacobs)

  • Researcher gives e.g. 4 digits and the participant must recall them in the correct order
  • If it's correct, the researcher reads out 5 digits and so on until the participant cannot recall the order correctly, determining their digital span
  • Found the mean span for digits = 9 and letters = 7
• Who researched into the capacity of LTM?

  Miller
• Describe research into the capacity of LTM (Miller)


  • Made observations of everyday practices e.g. noted things that came in 7s (musical scale, days of the week)
  • Suggests the span of STM is around 7 items (+/- 2)
  • People can recall 5 words and 5 letter by chunking
• Who researched into the duration of STM?


  Peterson and Peterson
• Describe research into the duration of STM (Peterson x2)

  • Students were given trigrams and 3 digit numbers to remember
  • Asked to count backwards from the 3 digit number until told to stop, preventing any mental rehearsal
  • Were told to stop after a different amount of time (retention interval)
  • Suggests STM has a short duration unless verbal rehearsal takes place
• Who researched into the duration of LTM?

  Bahrick
• Describe research into the duration of LTM (Bahrick)


  • High school yearbooks were obtained and recall was tested through photo recognition of 50 photos and a free recall test where participants recalled names of their graduating class
  • Those tested within 15 years: 90% accurate and after 48 years: 70% accurate
  • Shows LTM can last a long time
• Evaluation into the coding, capacity and duration of memory 


  • High external validity in Bahrick's study
  • Meaningless stimuli in Peterson's research
  • Lacking validity in Jacob's study
  • Not so many chunks in Miller's study